Flash Device model The Flash Device model is a timing model for a NAND flash device. More...

#include <flash_device.hh>

Inheritance diagram for gem5::FlashDevice:

Classes
struct	CallBackEntry

struct	FlashDeviceStats

struct	PageMapEntry
	Every logical address maps to a physical block and a physical page. More...

Public Member Functions
	FlashDevice (const FlashDeviceParams &)
	Initialize functions.

	~FlashDevice ()

DrainState	drain () override
	Checkpoint functions.

void	checkDrain ()
	Checkdrain; needed to enable checkpoints.

void	serialize (CheckpointOut &cp) const override
	Serialize; needed to create checkpoints.

void	unserialize (CheckpointIn &cp) override
	Unserialize; needed to restore from checkpoints.

Public Member Functions inherited from gem5::AbstractNVM
	AbstractNVM (const AbstractNVMParams &p)

virtual	~AbstractNVM ()

Public Member Functions inherited from gem5::SimObject
const Params &	params () const

	SimObject (const Params &p)

virtual	~SimObject ()

virtual void	init ()
	init() is called after all C++ SimObjects have been created and all ports are connected.

virtual void	loadState (CheckpointIn &cp)
	loadState() is called on each SimObject when restoring from a checkpoint.

virtual void	initState ()
	initState() is called on each SimObject when not restoring from a checkpoint.

virtual void	regProbePoints ()
	Register probe points for this object.

virtual void	regProbeListeners ()
	Register probe listeners for this object.

ProbeManager *	getProbeManager ()
	Get the probe manager for this object.

virtual Port &	getPort (const std::string &if_name, PortID idx=InvalidPortID)
	Get a port with a given name and index.

virtual void	startup ()
	startup() is the final initialization call before simulation.

DrainState	drain () override
	Provide a default implementation of the drain interface for objects that don't need draining.

virtual void	memWriteback ()
	Write back dirty buffers to memory using functional writes.

virtual void	memInvalidate ()
	Invalidate the contents of memory buffers.

void	serialize (CheckpointOut &cp) const override
	Serialize an object.

void	unserialize (CheckpointIn &cp) override
	Unserialize an object.

Public Member Functions inherited from gem5::EventManager
EventQueue *	eventQueue () const

void	schedule (Event &event, Tick when)

void	deschedule (Event &event)

void	reschedule (Event &event, Tick when, bool always=false)

void	schedule (Event *event, Tick when)

void	deschedule (Event *event)

void	reschedule (Event *event, Tick when, bool always=false)

void	wakeupEventQueue (Tick when=(Tick) -1)
	This function is not needed by the usual gem5 event loop but may be necessary in derived EventQueues which host gem5 on other schedulers.

void	setCurTick (Tick newVal)

	EventManager (EventManager &em)
	Event manger manages events in the event queue.

	EventManager (EventManager *em)

	EventManager (EventQueue *eq)

Public Member Functions inherited from gem5::Serializable
	Serializable ()

virtual	~Serializable ()

void	serializeSection (CheckpointOut &cp, const char *name) const
	Serialize an object into a new section.

void	serializeSection (CheckpointOut &cp, const std::string &name) const

void	unserializeSection (CheckpointIn &cp, const char *name)
	Unserialize an a child object.

void	unserializeSection (CheckpointIn &cp, const std::string &name)

Public Member Functions inherited from gem5::Drainable
DrainState	drainState () const
	Return the current drain state of an object.

virtual void	notifyFork ()
	Notify a child process of a fork.

Public Member Functions inherited from gem5::statistics::Group
	Group (Group parent, const char name=nullptr)
	Construct a new statistics group.

virtual	~Group ()

virtual void	regStats ()
	Callback to set stat parameters.

virtual void	resetStats ()
	Callback to reset stats.

virtual void	preDumpStats ()
	Callback before stats are dumped.

void	addStat (statistics::Info *info)
	Register a stat with this group.

const std::map< std::string, Group * > &	getStatGroups () const
	Get all child groups associated with this object.

const std::vector< Info * > &	getStats () const
	Get all stats associated with this object.

void	addStatGroup (const char name, Group block)
	Add a stat block as a child of this block.

const Info *	resolveStat (std::string name) const
	Resolve a stat by its name within this group.

void	mergeStatGroup (Group *block)
	Merge the contents (stats & children) of a block to this block.

	Group ()=delete

	Group (const Group &)=delete

Group &	operator= (const Group &)=delete

Public Member Functions inherited from gem5::Named
	Named (const std::string &name_)

virtual	~Named ()=default

virtual std::string	name () const

Private Types
enum	Actions { ActionRead , ActionWrite , ActionErase , ActionCopy }
	Defines the possible actions to the flash. More...

Private Member Functions
void	initializeMemory (uint64_t disk_size, uint32_t sector_size) override
	Device access functions Inherrited from AbstractNVM.

void	readMemory (uint64_t address, uint32_t amount, const std::function< void()> &event) override
	Access functions Access function to simulate a read/write access to the memory.

void	writeMemory (uint64_t address, uint32_t amount, const std::function< void()> &event) override

void	initializeFlash (uint64_t disk_size, uint32_t sector_size)
	Initialization function; called when all disk specifics are known.

void	accessDevice (uint64_t address, uint32_t amount, const std::function< void()> &event, Actions action)
	Flash action function.

void	actionComplete ()
	Event rescheduler.

Tick	remap (uint64_t logic_page_addr)
	FTL functionality.

Tick	accessTimes (uint64_t address, Actions accesstype)
	Access time calculator.

void	clearUnknownPages (uint32_t index)
	Function to indicate that a page is known.

bool	getUnknownPages (uint32_t index)
	Function to test if a page is known.

Private Attributes
uint64_t	diskSize
	Disk sizes in bytes.

const uint32_t	blockSize

const uint32_t	pageSize

const uint32_t	GCActivePercentage
	Garbage collection algorithm emulator.

const Tick	readLatency
	Access latencies.

const Tick	writeLatency

const Tick	eraseLatency

const enums::DataDistribution	dataDistribution
	Flash organization.

const uint32_t	numPlanes

struct FlashDeviceStats	stats
	RequestHandler stats.

uint32_t	pagesPerBlock
	Disk dimensions in pages and blocks.

uint32_t	pagesPerDisk

uint32_t	blocksPerDisk

uint32_t	planeMask

std::vector< uint32_t >	unknownPages
	when the disk is first started we are unsure of the number of used pages, this variable will help determining what we do know.

std::vector< struct PageMapEntry >	locationTable
	address to logic place has a block and a page field

std::vector< uint32_t >	blockValidEntries
	number of valid entries per block

std::vector< uint32_t >	blockEmptyEntries
	number of empty entries

std::vector< std::deque< struct CallBackEntry > >	planeEventQueue
	This vector of queues keeps track of all the callbacks per plane.

EventFunctionWrapper	planeEvent
	Completion event.

Additional Inherited Members
Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Static Public Member Functions inherited from gem5::SimObject
static void	serializeAll (const std::string &cpt_dir)
	Create a checkpoint by serializing all SimObjects in the system.

static SimObject *	find (const char *name)
	Find the SimObject with the given name and return a pointer to it.

static void	setSimObjectResolver (SimObjectResolver *resolver)
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

static SimObjectResolver *	getSimObjectResolver ()
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

Static Public Member Functions inherited from gem5::Serializable
static const std::string &	currentSection ()
	Gets the fully-qualified name of the active section.

static void	generateCheckpointOut (const std::string &cpt_dir, std::ofstream &outstream)
	Generate a checkpoint file so that the serialization can be routed to it.

Protected Member Functions inherited from gem5::Drainable
	Drainable ()

virtual	~Drainable ()

virtual void	drainResume ()
	Resume execution after a successful drain.

void	signalDrainDone () const
	Signal that an object is drained.

Protected Attributes inherited from gem5::SimObject
const SimObjectParams &	_params
	Cached copy of the object parameters.

Protected Attributes inherited from gem5::EventManager
EventQueue *	eventq
	A pointer to this object's event queue.

Detailed Description

Flash Device model The Flash Device model is a timing model for a NAND flash device.

It doesn't tranfer any data

Definition at line 57 of file flash_device.hh.

Member Enumeration Documentation

◆ Actions

enum gem5::FlashDevice::Actions

private

Defines the possible actions to the flash.

Enumerator
ActionRead
ActionWrite
ActionErase
ActionCopy	A copy involves taking all the used pages from a block and store it in another.

Definition at line 74 of file flash_device.hh.

Constructor & Destructor Documentation

◆ FlashDevice()

gem5::FlashDevice::FlashDevice ( const FlashDeviceParams & p )

Initialize functions.

Flash Device constructor and destructor.

Definition at line 65 of file flash_device.cc.

References actionComplete().

◆ ~FlashDevice()

gem5::FlashDevice::~FlashDevice ( )

Definition at line 145 of file flash_device.cc.

References DPRINTF.

Member Function Documentation

◆ accessDevice()

void gem5::FlashDevice::accessDevice	(	uint64_t	address,
		uint32_t	amount,
		const std::function< void()> &	event,
		Actions	action )

private

Flash action function.

Handles the accesses to the device.

The function determines when certain actions are scheduled and schedules an event that uses the callback function on completion of the action.

The access will be broken up in a number of page accesses. The number of page accesses depends on the amount that needs to be transfered. The assumption here is that the interface is completely ignorant of the page size and that this model has to figure out all of the transaction characteristics.

Check if the page is known and used. unknownPages is a bitmap of all the pages. It tracks wether we can be sure that the information of this page is taken into acount in the model (is it considered in blockValidEntries and blockEmptyEntries?). If it has been used in the past, then it is known.

previous part of the function found the times spend in different planes, now lets find the maximum to know when to callback the disk

If there are no events for this plane, then add the current time to the occupation time; otherwise, plan it after the last event. If by chance that event is handled in this tick, then we would still end up with the same result.

Definition at line 156 of file flash_device.cc.

References accessTimes(), ActionRead, ActionWrite, gem5::QARMA::amount, blockEmptyEntries, blockValidEntries, clearUnknownPages(), gem5::X86ISA::count, gem5::curTick(), DPRINTF, gem5::MipsISA::event, gem5::FlashDevice::FlashDeviceStats::fileSystemAccess, getUnknownPages(), gem5::MipsISA::index, locationTable, numPlanes, pageSize, pagesPerBlock, planeEvent, planeEventQueue, planeMask, gem5::FlashDevice::FlashDeviceStats::readAccess, gem5::FlashDevice::FlashDeviceStats::readLatency, remap(), gem5::EventManager::reschedule(), gem5::statistics::DistBase< Derived, Stor >::sample(), gem5::EventManager::schedule(), gem5::Event::scheduled(), stats, gem5::FlashDevice::CallBackEntry::time, gem5::Event::when(), gem5::FlashDevice::FlashDeviceStats::writeAccess, and gem5::FlashDevice::FlashDeviceStats::writeLatency.

Referenced by readMemory(), and writeMemory().

◆ accessTimes()

Tick gem5::FlashDevice::accessTimes	(	uint64_t	address,
		Actions	accesstype )

private

Access time calculator.

Calculates the accesstime per operation needed.

Just read the page

Write the page, and read the result

Erase and check wether it was successfull

Copy every valid page

Definition at line 395 of file flash_device.cc.

References ActionCopy, ActionErase, ActionRead, ActionWrite, blockValidEntries, DPRINTF, eraseLatency, readLatency, and writeLatency.

Referenced by accessDevice(), and remap().

◆ actionComplete()

void gem5::FlashDevice::actionComplete ( )

private

Event rescheduler.

When a plane completes its action, this event is triggered.

When a callback function was associated with that event, it will be called.

Search for a callback that is supposed to happen in this Tick

Invariant: All queued events are scheduled in the present or future.

To ensure that the follow-up action is executed correctly, the callback entry first need to be cleared before it can be called.

Found a callback, lets make it happen

Find when to schedule the planeEvent next

Schedule the next plane that will be ready (if any)

Definition at line 281 of file flash_device.cc.

References checkDrain(), gem5::curTick(), DPRINTF, numPlanes, planeEvent, planeEventQueue, gem5::EventManager::reschedule(), and gem5::Event::when().

Referenced by FlashDevice().

◆ checkDrain()

void gem5::FlashDevice::checkDrain ( )

Checkdrain; needed to enable checkpoints.

Definition at line 570 of file flash_device.cc.

References gem5::curTick(), DPRINTF, gem5::Draining, gem5::Drainable::drainState(), planeEvent, gem5::Drainable::signalDrainDone(), and gem5::Event::when().

Referenced by actionComplete().

◆ clearUnknownPages()

void gem5::FlashDevice::clearUnknownPages ( uint32_t index )

inlineprivate

Function to indicate that a page is known.

clearUnknownPages.

defines that a page is known and used unknownPages is a bitmap of all the pages. It tracks wether we can be sure that the information of this page is taken into acount in the model (is it considered in blockValidEntries and blockEmptyEntries?). If it has been used in the past, then it is known. But it needs to be tracked to make decisions about write accesses, and indirectly about copy actions. one unknownPage entry is a 32 bit integer. So if we have a page index, then that means that we need entry floor(index/32) (index >> 5) and we need to select the bit which number is equal to the remainder of index/32 (index%32). The bit is cleared to make sure that we see it as considered in the future.

Definition at line 445 of file flash_device.cc.

References gem5::MipsISA::index, and unknownPages.

Referenced by accessDevice().

◆ drain()

DrainState gem5::FlashDevice::drain ( )

overridevirtual

Checkpoint functions.

Drain; needed to enable checkpoints.

Implements gem5::Drainable.

Definition at line 554 of file flash_device.cc.

References DPRINTF, gem5::Drained, gem5::Draining, planeEvent, and gem5::Event::scheduled().

◆ getUnknownPages()

bool gem5::FlashDevice::getUnknownPages ( uint32_t index )

inlineprivate

Function to test if a page is known.

getUnknownPages.

Verify wether a page is known

Definition at line 456 of file flash_device.cc.

References gem5::MipsISA::index, and unknownPages.

Referenced by accessDevice().

◆ initializeFlash()

void gem5::FlashDevice::initializeFlash	(	uint64_t	disk_size,
		uint32_t	sector_size )

private

Initialization function; called when all disk specifics are known.

Initiates all the flash functions: initializes the lookup tables, age of the device, etc.

This can only be done once the disk image is known. Thats why it can't be done in the constructor.

Sanity information: check flash configuration

Garbage collection related

This is a bitmap. Every bit is a page unknownPages is a vector of 32 bit integers. If every page was an integer, the total size would be pagesPerDisk; since we can map one page per bit we need ceil(pagesPerDisk/32) entries. 32 = 1 << 5 hence it will do to just shift pagesPerDisk five positions and add one. This will allocate one integer to many for this data structure in the worst case.

Definition at line 103 of file flash_device.cc.

References blockEmptyEntries, blockSize, blocksPerDisk, blockValidEntries, gem5::X86ISA::count, dataDistribution, diskSize, DPRINTF, locationTable, pageSize, pagesPerBlock, pagesPerDisk, and unknownPages.

Referenced by initializeMemory().

◆ initializeMemory()

void gem5::FlashDevice::initializeMemory	(	uint64_t	disk_size,
		uint32_t	sector_size )

inlineoverrideprivatevirtual

Device access functions Inherrited from AbstractNVM.

Implements gem5::AbstractNVM.

Definition at line 118 of file flash_device.hh.

References initializeFlash().

◆ readMemory()

void gem5::FlashDevice::readMemory	(	uint64_t	address,
		uint32_t	amount,
		const std::function< void()> &	event )

inlineoverrideprivatevirtual

Access functions Access function to simulate a read/write access to the memory.

Once the action has completed, the Callback event should be called. Putting a NULL pointer as callback is valid syntax, and should result in the simulation of the access, but with no callback to the higher layer. This may be used to occupy the device, such that next actions will be delayed. The read/write function will schedule the incoming requests on a first come first serve basis.

Parameters

address	The logical address to a location in the Non-volatile memory.
amount	The amount of data transfered from the NVM in bytes
event	A pointer to a callback function that will perform the actions taken by the disk controller on successfull completion of the data transfer between the disk and the disk controller.

Implements gem5::AbstractNVM.

Definition at line 124 of file flash_device.hh.

References accessDevice(), ActionRead, gem5::QARMA::amount, and gem5::MipsISA::event.

◆ remap()

Tick gem5::FlashDevice::remap ( uint64_t logic_page_addr )

private

FTL functionality.

Handles the remapping of the pages.

It is a (I hope) sensible statistic approach. asumption: garbage collection happens when a clean is needed (may become stochastic function).

Are there any empty left in this Block, or do we need to do an erase

Definition at line 342 of file flash_device.cc.

References accessTimes(), ActionCopy, ActionErase, ActionWrite, blockEmptyEntries, gem5::X86ISA::count, DPRINTF, GCActivePercentage, locationTable, pagesPerBlock, pagesPerDisk, stats, and gem5::FlashDevice::FlashDeviceStats::totalGCActivations.

Referenced by accessDevice().

◆ serialize()

void gem5::FlashDevice::serialize ( CheckpointOut & cp ) const

overridevirtual

Serialize; needed to create checkpoints.

Implements gem5::Serializable.

Definition at line 507 of file flash_device.cc.

References blockEmptyEntries, blockValidEntries, gem5::X86ISA::count, gem5::csprintf(), locationTable, gem5::paramOut(), planeMask, SERIALIZE_CONTAINER, SERIALIZE_SCALAR, and unknownPages.

◆ unserialize()

void gem5::FlashDevice::unserialize ( CheckpointIn & cp )

overridevirtual

Unserialize; needed to restore from checkpoints.

Implements gem5::Serializable.

Definition at line 530 of file flash_device.cc.

References blockEmptyEntries, blockValidEntries, gem5::X86ISA::count, gem5::csprintf(), locationTable, gem5::paramIn(), planeMask, unknownPages, UNSERIALIZE_CONTAINER, and UNSERIALIZE_SCALAR.

◆ writeMemory()

void gem5::FlashDevice::writeMemory	(	uint64_t	address,
		uint32_t	amount,
		const std::function< void()> &	event )

inlineoverrideprivatevirtual

Implements gem5::AbstractNVM.

Definition at line 131 of file flash_device.hh.

References accessDevice(), ActionWrite, gem5::QARMA::amount, and gem5::MipsISA::event.

Member Data Documentation

◆ blockEmptyEntries

std::vector<uint32_t> gem5::FlashDevice::blockEmptyEntries

private

number of empty entries

Definition at line 196 of file flash_device.hh.

Referenced by accessDevice(), initializeFlash(), remap(), serialize(), and unserialize().

◆ blockSize

const uint32_t gem5::FlashDevice::blockSize

private

Definition at line 161 of file flash_device.hh.

Referenced by initializeFlash().

◆ blocksPerDisk

uint32_t gem5::FlashDevice::blocksPerDisk

private

Definition at line 182 of file flash_device.hh.

Referenced by initializeFlash().

◆ blockValidEntries

std::vector<uint32_t> gem5::FlashDevice::blockValidEntries

private

number of valid entries per block

Definition at line 194 of file flash_device.hh.

Referenced by accessDevice(), accessTimes(), initializeFlash(), serialize(), and unserialize().

◆ dataDistribution

const enums::DataDistribution gem5::FlashDevice::dataDistribution

private

Flash organization.

Definition at line 173 of file flash_device.hh.

Referenced by initializeFlash().

◆ diskSize

uint64_t gem5::FlashDevice::diskSize

private

Disk sizes in bytes.

Definition at line 160 of file flash_device.hh.

Referenced by initializeFlash().

◆ eraseLatency

const Tick gem5::FlashDevice::eraseLatency

private

Definition at line 170 of file flash_device.hh.

Referenced by accessTimes().

◆ GCActivePercentage

const uint32_t gem5::FlashDevice::GCActivePercentage

private

Garbage collection algorithm emulator.

Definition at line 165 of file flash_device.hh.

Referenced by remap().

◆ locationTable

std::vector<struct PageMapEntry> gem5::FlashDevice::locationTable

private

address to logic place has a block and a page field

Definition at line 192 of file flash_device.hh.

Referenced by accessDevice(), initializeFlash(), remap(), serialize(), and unserialize().

◆ numPlanes

const uint32_t gem5::FlashDevice::numPlanes

private

Definition at line 174 of file flash_device.hh.

Referenced by accessDevice(), and actionComplete().

◆ pageSize

const uint32_t gem5::FlashDevice::pageSize

private

Definition at line 162 of file flash_device.hh.

Referenced by accessDevice(), and initializeFlash().

◆ pagesPerBlock

uint32_t gem5::FlashDevice::pagesPerBlock

private

Disk dimensions in pages and blocks.

Definition at line 180 of file flash_device.hh.

Referenced by accessDevice(), initializeFlash(), and remap().

◆ pagesPerDisk

uint32_t gem5::FlashDevice::pagesPerDisk

private

Definition at line 181 of file flash_device.hh.

Referenced by initializeFlash(), and remap().

◆ planeEvent

EventFunctionWrapper gem5::FlashDevice::planeEvent

private

Completion event.

Definition at line 202 of file flash_device.hh.

Referenced by accessDevice(), actionComplete(), checkDrain(), and drain().

◆ planeEventQueue

std::vector<std::deque<struct CallBackEntry> > gem5::FlashDevice::planeEventQueue

private

This vector of queues keeps track of all the callbacks per plane.

Definition at line 199 of file flash_device.hh.

Referenced by accessDevice(), and actionComplete().

◆ planeMask

uint32_t gem5::FlashDevice::planeMask

private

Definition at line 184 of file flash_device.hh.

Referenced by accessDevice(), serialize(), and unserialize().

◆ readLatency

const Tick gem5::FlashDevice::readLatency

private

Access latencies.

Definition at line 168 of file flash_device.hh.

Referenced by accessTimes().

◆ stats

struct FlashDeviceStats gem5::FlashDevice::stats

private

RequestHandler stats.

Definition at line 177 of file flash_device.hh.

Referenced by accessDevice(), and remap().

◆ unknownPages

std::vector<uint32_t> gem5::FlashDevice::unknownPages

private

when the disk is first started we are unsure of the number of used pages, this variable will help determining what we do know.

Definition at line 190 of file flash_device.hh.

Referenced by clearUnknownPages(), getUnknownPages(), initializeFlash(), serialize(), and unserialize().

◆ writeLatency

const Tick gem5::FlashDevice::writeLatency

private

Definition at line 169 of file flash_device.hh.

Referenced by accessTimes().

The documentation for this class was generated from the following files:

dev/arm/flash_device.hh
dev/arm/flash_device.cc

Classes

Public Member Functions

Private Types

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ Actions

Constructor & Destructor Documentation

◆ FlashDevice()

◆ ~FlashDevice()

Member Function Documentation

◆ accessDevice()

◆ accessTimes()

◆ actionComplete()

◆ checkDrain()

◆ clearUnknownPages()

◆ drain()

◆ getUnknownPages()

◆ initializeFlash()

◆ initializeMemory()

◆ readMemory()

◆ remap()

◆ serialize()

◆ unserialize()

◆ writeMemory()

Member Data Documentation

◆ blockEmptyEntries

◆ blockSize

◆ blocksPerDisk

◆ blockValidEntries

◆ dataDistribution

◆ diskSize

◆ eraseLatency

◆ GCActivePercentage

◆ locationTable

◆ numPlanes

◆ pageSize

◆ pagesPerBlock

◆ pagesPerDisk

◆ planeEvent

◆ planeEventQueue

◆ planeMask

◆ readLatency

◆ stats

◆ unknownPages

◆ writeLatency